This invention concerns improvements in the processing of video image signals to achieve so-called digital video effects.
In such processing, each field frame of a television image is stored as a series of discrete digital values or pixels containing the luminance or chrominance information of the original signal and obtained by sampling the original signal at an appropriate pixel repetition rate. The original signal may be reproduced by scanning the store, or, by addressing the store in appropriately timed relation to synchronising signals defining the television raster, selected image information can be retrieved from the store and displayed on a television screen in any desired position or orientation. Such retrieved information may be combined with other image information to produce a pattern or collage or discrete images, and by moving the boundaries between respective patterns containing the separate picture information, various effects can be achieved.
One such effect is that known as "Multifreeze" wherein an image area that is shown as moving against a background is caused to leave a trail of frozen images behind it.